PianoTech Archive

From "David Ilvedson" <ilvey@sbcglobal.net>

List,



Is there a clear cut way to position the duplex bars on a Steinway?   This is 100 year old B I'm restringing.   Top treble sections only.   I can position as I found it but is there a measurement from the bridge pins...?



David Ilvedson, RPT

Pacifica, CA 94044

From <pianoguru@cox.net>

David, et al,

I cannot speak to the specific make, model, and era of your piano, but typical of pianos with this type of duplexer, the distance from the back bridge pin to the duplexer at note 88 is equal to the speaking length.    One can go a step further, and after stringing, nudge the duplexer in or out, to "tune" the duplex length to sound in unison with the speaking length at note 88.  Whether one believes that "tuning" the duplexer is effective, it was probably the design intent, if you find that the original position of the duplexer suggests this relationship between the duplex length and the speaking length.

This 1:1 relationship can only be maintained for a few note below 88.  You can clearly see where the duplex length suddenly becomes shorter, around note 80, or so.  Measuring the speaking lengths and duplex lengths, you will likely fine a whole-number relationship, with ratios following a sequence something like 1:1, then 2:3, 1:2, 1:3, and 1:4.  The rationale behind these relationships is to make the fundamental frequency of the sympathetic vibration of the duplex length correspond to a higher partial of the speaking length, or at least to have a harmonic relationship to the speaking length.

There are exceptions.  Some builders make this distance significantly shorter to effectively add to the stiffness of the soundboard in the high treble.  Bear in mind that significantly shortening the tail length has implications for the balance between front and back downbearing, not so much at note 88, but throughout the scale.  Changes in the crown will have a huge impact on a very short tail length, while having a negligible impact on a relatively long speaking length.

Other makers would prefer to use the position of the duplexer to refine the downbearing, moving it in or out to increase or decrease downbearing.  If this were the intended function, then the term, "Duplexer," would be a misnomer.  

It is not uncommon to see three sections with "duplexers," with the lowest (tenor) section being muted out with stringing braid or felt.   In these cases, it may have been the intent that the duplexer in the top two section truly function as duplexers, while in the tenor section its function is simply that of a string rest to facilitated controlling downbearing.

I have seen Steinways with hardwood tapered shims under the duplexer, and cut to the same shape as the duplexer.  Whether this was done in the factory or by a rebuilder, presumably the shim was added to control downbearing, while preserving the duplex function of the duplexer.

Frank Emerson

From Erwinspiano@aol.com

Hi Frank
  Although you are correct about this for many pianos, the Steinway  B's rear 
duplex string length doesn't follow this. it's an octave higher
  Dale
 
 
David, et al,

I cannot speak to the specific make, model, and era  of your piano, but 
typical of pianos with this type of duplexer, the  distance from the back bridge 
pin to the duplexer at note 88 is equal to the  speaking length.    One can go a 
step further, and after  stringing, nudge the duplexer in or out, to "tune" 
the duplex length to sound in  unison with the speaking length at note 88.  
Whether one believes that  "tuning" the duplexer is effective, it was probably 
the design intent, if you  find that the original position of the duplexer 
suggests this relationship  between the duplex length and the speaking length.


 



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From "David Ilvedson" <ilvey@sbcglobal.net>

So half the speaking length...



David Ilvedson, RPT

Pacifica, CA 94044









Original message

From: Erwinspiano@aol.com

To: pianotech@ptg.org

Received: 1/3/2008 2:30:47 AM

Subject: Re: duplex position





  Hi Frank

  Although you are correct about this for many pianos, the Steinway B's rear duplex string length doesn't follow this. it's an octave higher

  Dale





David, et al,



I cannot speak to the specific make, model, and era of your piano, but typical of pianos with this type of duplexer, the distance from the back bridge pin to the duplexer at note 88 is equal to the speaking length.    One can go a step further, and after stringing, nudge the duplexer in or out, to "tune" the duplex length to sound in unison with the speaking length at note 88.  Whether one believes that "tuning" the duplexer is effective, it was probably the design intent, if you find that the original position of the duplexer suggests this relationship between the duplex length and the speaking length.

















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From "David Love" <davidlovepianos@comcast.net>

Generally, you don't have that much room to play around with these.  If you
are tuning them then you need to hit some whole number relationship.  If
not, then the farther back you can push them (toward the hitch pins) the
better, keeping in mind that the bearing will change depending on where they
end up.  Tuning aside, I find that Steinways usually don't have a long
enough backscale.  The shorter the backscale, the lighter the bearing needs
to be and sometimes those two requirements can be at odds, especially when a
compression style board is asking for more bearing to get things stiff
enough which ends up just tying down the bridge because of the short
backscale and around and around.  Choose your poison.   

 

David Love
davidlovepianos@comcast.net
www.davidlovepianos.com 



                                                

					
                                                    

        
                                                
				
                                                

                                                    
                                                        
                                                        Original Message
                                                
                                                Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf
Of David Ilvedson
Sent: Thursday, January 03, 2008 8:59 AM
To: pianotech@ptg.org
Subject: Re: duplex position

 

 

So half the speaking length...

David Ilvedson, RPT
Pacifica, CA 94044

  _____  

Original message
From: Erwinspiano@aol.com
To: pianotech@ptg.org
Received: 1/3/2008 2:30:47 AM
Subject: Re: duplex position




  Hi Frank

  Although you are correct about this for many pianos, the Steinway B's rear
duplex string length doesn't follow this. it's an octave higher

  Dale

 

 

David, et al,

I cannot speak to the specific make, model, and era of your piano, but
typical of pianos with this type of duplexer, the distance from the back
bridge pin to the duplexer at note 88 is equal to the speaking length.
One can go a step further, and after stringing, nudge the duplexer in or
out, to "tune" the duplex length to sound in unison with the speaking length
at note 88.  Whether one believes that "tuning" the duplexer is effective,
it was probably the design intent, if you find that the original position of
the duplexer suggests this relationship between the duplex length and the
speaking length.

 

 





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ways to stay in shape for winter. 

From ricb@pianostemmer.no

If it is really of no consequence, you could toss them and drill and
install
vertical hitches. That would allow you to adjust the rear component
for
downbearing. 

FWIW,

Alan

From Richard Brekne <ricb@pianostemmer.no>

Hi Frank.

Sorry about the accidental posting to pianotech.  That said I'd have to 
agree with your assessment that duplexers not inconsequential. As to 
what one prefers or doesn't... well to each his own as far as I am 
concerned.  I tend to like piano that have them... with few exceptions.  
I doubt your position is an unpopular one to take since all but a 
handful of the piano builders / designers I've met opt for them.  I 
think its fair to say however that the use of vertical hitch pins 
without duplexers can be successfully used in piano design as well.

Curious as too your objection to vertical hitch pins.  Personally I dont 
see the big deal either way...

Cheers
RicB

    I guess there is a parallel thread with CAUT that I have not seen. 
    I would have to disagree with the notion that duplexers are of no
    consequence.  I have designed and built pianos with and without
    vertical hitch pins.  At this point in my experience, I have no use
    for vertical hitch pins and do prefer a duplexer style of
    construction.  I suppose that is an unpopular position to take, but
    it is mine.

    Frank Emerson

From Richard Brekne <ricb@pianostemmer.no>

Hi Frank.

First let me say I have to admire the calm and dispassionate way in 
which you keep presenting your perspectives here. A very refreshing 
exception to the rule.

I was particularly interested in two points you make below. First the 
one about the Baldwin claim to be able to take care of duplex lengths 
despite the "third string" always being rather impossible. The 
interesting bit is that they saw fit to defend that duplex issue at all. 
This is not to foreign to argumentation I have heard here... that one 
can design back lengths in that <<sound better>> then tuned duplexed 
lengths by the use of vertical hitch pins. Such a claim directly 
contradicts any claim that placement of duplexers is meaningless. Yet 
both these claims seem to be made by the same folks in certain places of 
the world... and I don't just mean here and I don't just mean on one or 
the other side of the issue.

The other bit I find very interesting is your point about the stresses 
on the plate a vertical hitch pins creates. I take it as a given that 
Baldwin figured this into their equation when designing their plates... 
but simply installing vertical hitch pins in a plate where this was not 
designed into the thing to begin with does strikes me as risky at best. 
A lot can occur besides simple plate failure. The issue of field techs 
being able to move adjust the strings position on the vertical hitch pin 
has been up many times... and has a certain degree of validity IMHO. 
Indeed that was one of the reasons given why S&S stopped making 
adjustable front duplex bars way back when.

One of the things I appreciate so very much about Ron Overs approach 
towards giving advice on more advanced redesign issues touches directly 
on this kind of thing. He has this big disclaimer side warning folks on 
all levels that they simply need to know what they are doing before 
making such changes. More or less underlines in bold that its far too 
easy to overestimate ones own knowledge.

Anyways... thanks for the informative posting.

Cheers
RicB



        ---- Richard Brekne <ricb at pianostemmer.no> wrote:
         > I doubt your position is an unpopular one to take since all
        but a
         > handful of the piano builders / designers I've met opt for
        them. I
         > think its fair to say however that the use of vertical hitch
        pins
         > without duplexers can be successfully used in piano design as
        well.


    Yes, duplexers, as opposed to vertical hitch pins, are more common
    in modern production of new pianos, but the reverse seems to be the
    preference among rebuilders/redesigners on this list.

    I would also agree that vertical hitch pins have successfully been
    used. As I said, I have used them myself, and have been satisfied
    with the results. Still, in the final analysis, I prefer traditional
    duplexers to vertical hitch pins in my current work.

         > Curious as too your objection to vertical hitch pins.
        Personally I don?t
         > see the big deal either way...


    It's not a big deal either way, but here are a few of my reasons for
    my preference:

    Baldwin claimed to preserve duplex scaling with vertical hitch pins.
    That works (to some extent) with strings that are common to a single
    unison, but strings that are shared by two unisons can only satisfy
    the tail length of one note, but not the other. More importantly,
    the duplex, tail length, is fixed (not adjustable). Getting the
    "duplex/tail length" in the "ball park" is not good enough for me.
    If it cannot be "tuned" to the desired relationship to the speaking
    length, it's not worth bothering with it.

    Vertical hitch pins transfer the force of the string tension high
    enough on the pins to create a radically different leverage on the
    plate. Where the string tension is applied to the bottom of the
    hitch pin, the forces applied to the plate are minimal. Where the
    force of the string tension is applied 6-12mm above to surface of
    the plate, the mechanical (dis)advantage of the leverage applies a
    significantly greater stress on the plate casting. I have seen plate
    cracks along the line of vertical hitch pins, where it would never
    have occurred with traditional hitch pins.

    I remember a time when the rolled pins where not hardened to the
    specified hardness. I don't remember how many pianos were effected,
    but I would say they was in the hundreds. The pins bent, and every
    piano effected had to be reworked. Since this was an error of a
    vendor of a vendor, it was not an easy problem to fix.

    Since setting bearing was deferred until after the string is drawn
    to full tension, there is a wide margin of error. I remember pianos
    soundboards failing with a loud bang, the soundboard pulling up, and
    breaking free from the belly rail in the high treble. This would
    never have happened with traditional hitch pins.

    Finally, vertical hitch pins open the piano to devastating results
    from unknowledgeable techs making misguided changes in down bearing.
    I hate to say this on a piano tech list, but I have seen the results
    of such misguided movement of the strings on vertical hitch pins. I
    would prefer to permanently set the bearing in the manufacturing
    process, in a way that cannot be compromised by well-meaning, but
    misguided techs.

    Frank Emerson

From "William R. Monroe" <pianotech@a440piano.net>

Hi Ric,

I think what you say makes sense, but I don't think it's safe to say that 
just because it's intuitive, a particular manufacturer took that step.  I'd 
think it would be just as easy to say that most if not all plates can easily 
withstand the pressures of vertical hitches with the strings "riding high." 
Maybe someone knows if this was really a design consideration at Baldwin. 
Del?

William R. Monroe


From: "Richard Brekne" <ricb@pianostemmer.no>
SNIP

> The other bit I find very interesting is your point about the stresses on 
> the plate a vertical hitch pins creates. I take it as a given that Baldwin 
> figured this into their equation when designing their plates... but simply 
> installing vertical hitch pins in a plate where this was not designed into 
> the thing to begin with does strikes me as risky at best.

SNIP

> Cheers
> RicB

From Ron Nossaman <rnossaman@cox.net>

> I'd think it would be just as easy to say that most if not all 
> plates can easily withstand the pressures of vertical hitches with the 
> strings "riding high." Maybe someone knows if this was really a design 
> consideration at Baldwin. Del?


Like anything, it depends, and as usual, no one has proposed 
mindless replacement of standard hitches with vertical without 
some intelligent consideration behind it - as it's being 
argued against.

This has all been covered before, and is in the archives.

First: With the plate and bridge heights accurately set so the 
strings are in a more reasonable 2-4mm height range on the 
hitches, or even up to the height of the aliquot the vertical 
hitch replaced, rather than the 10+ that seems to be assumed, 
there isn't a huge lot of added torque on the plate.

Second: If you rearrange the hitch pattern so they aren't in 
the original "break here" straight line perforation pattern, 
you considerably decrease the likelihood of breaking anything. 
See photos.

Third: If you keep the hitches as far from the plate edge as 
is feasible, you add further safety factor.

Fourth: If you have a minimum allowable plate thickness, like, 
say, 11mm, you won't be installing these things where it's 
dangerous to do so.

Fifth: If you only drill your pilot holes a couple of 
thousandths of an inch undersized for roll pins, rather than 
ten, you can drive the pins in easily with a small light 
hammer rather than mauling the plate with a sledge to install 
them.

Sixth: If you set the string height at 4mm on the pins as you 
string it, you'll have some positive bearing when you pull the 
thing up to pitch the first time. You did, after all, 
determine beforehand where the bridge would end up under 
bearing load and set the plate height accordingly, right? 
Remember, you're in (or are) a small rebuilding shop where 
you're responsible for doing your own thinking, not in a large 
factory where you're going through the same narrow operation 
infinitely on autopilot without verification that the 
prerequisites to your current operation have been met by 
someone else. So if you pull the soundboard up off the rim, 
it's safe to blame personal stupidity rather than the vertical 
hitches.

Yes, there is still a chance of plate breakage, just as there 
is when you restring a piano with no modifications whatsoever. 
If it's a big concern, don't install vertical hitches. 
Vertical hitches in the bass alone can improve bass response 
with a shorter than optimal back scale, and most bass hitch 
risers are heavy enough to take almost anything you could do 
to them.

Ron N

From Richard Brekne <ricb@pianostemmer.no>

I dont think anyone has accused anyone at all proposing mindless 
anything.... just raised the point that due caution has perhaps not been 
underlined enough at times. As for arguing against vertical hitch 
pins... strikes me as more then obvious that all the posts that reflect 
a preference for standard hitch pin and back duplex systems include 
clear statements as to the viability of an informed approach to vertical 
hitch pins. I still see nothing, having read closely,  anything in 
anyones posts on either side of the issue has written that shows any 
inherent overall advantages of one system over the other performance 
wise.  There is a clear potential danger of mis-use of vertical hitch 
pins to be sure... but that kind of thing comes with the territory. Give 
a field tech the ability to change a design parameter and you give 
him/her the ability to muck it up.... old news.

Cheers
RicBB



    Like anything, it depends, and as usual, no one has proposed
    mindless replacement of standard hitches with vertical without
    some intelligent consideration behind it - as it's being
    argued against.

From <pianoguru@cox.net>

---- ricb@pianostemmer.no wrote: 
> If it is really of no consequence, 

I guess there is a parallel thread with CAUT that I have not seen.  I would have to disagree with the notion that duplexers are of no consequence.  I have designed and built pianos with and without vertical hitch pins.  At this point in my experience, I have no use for vertical hitch pins and do prefer a duplexer style of construction.  I suppose that is an unpopular position to take, but it is mine.

Frank Emerson